Plenum LAN cables are formed by assembling together four twisted pairs of insulated copper wires, in which each twisted pair comprises a copper wire coated with a white colored fluoropolymer layer associated with a copper wire coated with a blue, green, orange or brown colored fluoropolymer.
Said brown colored fluoropolymer layer is typically a foamed layer obtained by foaming a polymer composition comprising fluoropolymer, a nucleating agent and iron oxide pigments, said pigments being basically used as standard brown pigments in such electrical cables.
However, it was found that upon foaming conditions, the presence of iron oxide pigments activates the thermal degradation of the fluoropolymer and, consequently promotes melt viscosity variations leading to an unstable flow during the extrusion process.
Hence, the brown foamed layer obtained by said unstable foaming process presents insulation defects, degraded dielectric properties as well as discoloration. The manufacturing conditions of the brown LAN insulated wire are thus limited, and an important amount of scrapped material is generated during the extrusion process.